The present invention is related to Japanese patent application No. Hei. 11-367125, filed Dec. 24, 1999; 2000-81610, filed Mar. 23, 2000 the contents of which are incorporated herein by reference.
The present invention relates to a motor vehicle alternator, and more particularly, to a motor vehicle alternator that prevents hunting of the rotational speed of the engine during idle state.
A decrease in rotational speed (hereinafter referred to as an idle rotational speed) of a motor vehicle alternator during vehicle idle will cause torque generated by the engine to be reduced. For this reason, the alternator drive torque (hereinafter also referred to as load torque) viewed from the engine will in turn increase due to the connection of an electrical load. For example, a large amount of starting current of a compressor drive motor is used for air conditioning within the vehicle. This will result in a hunting phenomenon in which the idle rotational speed becomes unstable and fluctuates.
Hunting of the rotational speed of the engine can cause the battery voltage to fluctuate more significantly, leading to various abnormal conditions and presenting a difficulty in maintaining idle operation or the like.
To prevent hunting of motor vehicle alternators of this type, various techniques have been conventionally suggested which allow adjustment of the control voltage according to a change in rotational speed.
Japanese Unexamined Patent Publication No. 7111, published 1979, suggested that the control voltage of an alternator should be reduced according to the rate of change in speed (a differential value) during deceleration of the engine (for negative differential values of rotational speed of the engine). On the other hand, during engine acceleration (for positive differential values of rotational speed of the engine), the voltage should be increased according to the rate of change in speed (a differential value).
Japanese Unexamined Patent Publication No. 87636, published 1985, applied for by the present inventor suggested that the amount of generated electricity should be kept below a predetermined value for a certain time during which the idle rotational speed recovered from the point of an increase in electrical load.
Japanese Patent Publication No. 55040 of 1994 applied for by the present inventor suggested that the control voltage should be increased in proportion to the degree of acceleration while increasing the rotational speed of the engine (under acceleration), while being delayed for a predetermined time relative to an increase in rotational speed of the engine.
Japanese Unexamined Patent Publication No. 327199, published 1997, suggested that a target voltage should be set to a certain low value less than a steady state target voltage during engine acceleration. On the other hand, during deceleration of the engine, the target voltage should be set to a certain high value higher than the steady state target voltage.
However, the following problems have been found to occur even with the aforementioned various prior-art techniques. First, these anti-hunting techniques change the control voltage of a regulator according to a change in rotational speed of the engine. Thus, the change of the rotational speed of the engine is associated with the change of the control voltage irrespective of the condition of the electric circuitry comprising the battery, electrical loads, and the alternator. For this reason, the condition of the electric circuitry was not taken into account and therefore the techniques were without validity in some cases. For example, it was not easy to take corrective action appropriately when the battery voltage recovered earlier than expected during acceleration or when the voltage recovered slower than expected due to a deep discharge regardless of substantial completion of acceleration. Furthermore, it was necessary to add signals such as a battery voltage to control parameters in addition to the aforementioned rotational speed of the engine, thus making the circuit processing complicated.
Furthermore, the aforementioned various conventional techniques provided a sudden variation in output or in drive torque (load torque) of the alternator during transitions of the rotational speed of the engine. The transitions include a transition from a steady state mode to a deceleration mode, a transition from the deceleration mode to an acceleration mode, and a transition near the point of completion of the acceleration mode. Such a sudden change in output of the alternator would cause a sudden change in torque and thereby a shock. The change would also readily cause heavy current charging to or heavy current discharging from batteries upon generation of high output, leading to a drop in charging efficiency or an increase in loss of power distribution.
In a first aspect of the invention, the controller sets the control voltage to an acceleration control voltage higher than the battery voltage by a predetermined voltage difference xcex94V1, within a range of voltages higher than the battery voltage and less than the steady state control voltage, during a acceleration during low speeds with the rotational speed being equal to or less than a predetermined value and a rate of increase in the rotational speed being equal to or greater than a predetermined value. This control can be called a mode for supressing rates of increase in battery voltage or a charge supression mode. Control of this type may be executed prior to control which employs the steady state control voltage as a control voltage, thereby preferably realizing control.
That is, according to this control, the control voltage is set higher than the battery voltage by a predetermined voltage difference xcex94V1 in the recovery process of the rotational speed of the engine. In this process, the rotational speed of the engine and the battery voltage are decreased due to the connection of electrical loads, and the rotational speed of the engine is increased due to an increase in fuel injection provided subsequently by the engine control system. Also, the predetermined voltage difference xcex94V1 ranges from 0.1V to 0.15V, and may be kept at a constant value during acceleration during low speeds. Alternatively, for example, the difference may be increased from the earlier stage to the later stage of acceleration during low speeds.
In another aspect, the control voltage is further set to a deceleration control voltage lower than the battery voltage by a predetermined voltage difference xcex94V2. This is carried out after the rotational speed of the engine has decreased below a first predetermined rotational speed value N1 within a period of deceleration during low speeds immediately preceding the aforementioned acceleration during low speeds. The control of this type can be referred to as a battery voltage drop adjustment mode or a discharge suppression mode which means not more than the suppression of discharge of the battery. Moreover, the control is desirably executed prior to the control which employs the steady state control voltage as a control voltage.
The predetermined voltage difference xcex94V2 ranges from 0.01V to 0.1V, and may be kept at a constant value during deceleration during low speeds. Alternatively, for example, the difference may be increased being operatively associated with a decrease in rotational speed of the engine or a drop in battery voltage.
That is, this arrangement employs a gradual decrease in control voltage during deceleration. This is carried out at the later stage of during deceleration during low speeds in which a smaller amount of the alternator output and torque produced by the engine is provided. The control voltage is thereby maintained to prevent the battery from being discharged while the rotational speed of the engine has decreased slightly and allowable power generation capacity is available at the earlier stage of during deceleration during low speeds. When the rotational speed of the engine decreases more than this, the control voltage is decreased, being operatively associated with a drop in battery voltage which requests that the battery discharges. Also, this arrangement does not allow the control voltage to be reduced all at once even after the rotational speed of the engine has been decreased below the first predetermined rotational speed value N1. For this reason, the drive torque (load torque) of the alternator will not be suddenly changed.
In another aspect of the invention, the predetermined voltage difference xcex94V1, between a voltage given at a minimum rotational speed value Nmin, at which during deceleration during low speeds is shifted to acceleration during low speeds, and a voltage at the subsequent rotational speed of the engine being equal to or greater than a second predetermined rotational speed value N2, is set to a voltage less than the predetermined voltage difference xcex94V1 during the subsequent acceleration during low speeds. Accordingly, power generation and charging of the battery are prevented to increase the rotational speed of the engine during the earlier stage in the recovery process of the rotational speed of the engine where the outputs of the engine torque and the alternator are not sufficient. At the same time, a sudden increase in drive torque (load torque) of the alternator viewed from the engine is prevented when during deceleration during low speeds is shifted to acceleration during low speeds. Furthermore, a sudden increase in battery charging current is prevented. This makes it possible to realize a smooth increase in engine load torque.
In another aspect, the controller further allows the predetermined voltage difference xcex94V1 to increase at a later stage rather than at an earlier stage of acceleration during low speeds. In another aspect, the control voltage is set to a deceleration control voltage less than the battery voltage by the predetermined voltage difference xcex94V2. This is carried out during a period of deceleration during low speeds with the rotational speed, immediately preceding the rotational speed of the engine is increased, being equal to or less than a predetermined value and the rate of decrease in rotational speed being equal to or greater than a predetermined value.
This makes it very possible to prevent a sudden increase in drive torque (load torque) of the alternator viewed from the engine, and the predetermined voltage difference xcex94Vxe2x80x99increases at a later stage rather than at an earlier stage of during deceleration during low speeds. Thus, the battery is prevented from being discharged by generating a relatively large amount of power by the alternator. This is done at the earlier stage of acceleration during low speeds with a decrease in rotational speed of the engine being still small. That is, this is done when the engine torque and the output of the alternator are still sufficient. On the other hand, consider the later stage of acceleration during low speeds where a smaller decrease occurs in rotational speed of the engine. that is, this happens when the engine torque and the output of the alternator have become insufficient. In this stage, power generation by the alternator is prevented to compensate for shortage in power by discharging the battery, thereby preventing a sudden decrease of the rotational speed of the engine.
Also, said increasing of the predetermined voltage difference xcex94V2 is continuously operatively associated with a decrease in rotational speed of the engine, thereby making it possible to smooth still more the change in drive torque (load torque) of the alternator viewed from the engine.
In another aspect of the invention, the controller for allowing the battery voltage to approach a control voltage includes a first setting means for setting the control voltage to a predetermined steady state control voltage, and second setting means for setting the control voltage to an acceleration control voltage higher than the battery voltage by a predetermined voltage difference xcex94V1. This voltage is within a range of voltages higher than the battery voltage and less than the steady state control voltage, during acceleration during low speeds with the rotational speed of the engine being equal to or less than a predetermined value and a rate of increase in the rotational speed being equal to or greater than a predetermined value.
In such an arrangement, when the second setting means employs the acceleration control voltage as the control voltage, more controlled power generation is carried out than when the control voltage is at the steady state control voltage. Consequently, while the battery is being charged, it becomes possible to make the load provided by the alternator to the engine lower than the load provided under the steady state control voltage.
To achieve the aforementioned object, the following method can be employed in a method for controlling a motor vehicle alternator wherein a rotational speed of an engine and a battery voltage are input, and field current is controlled so as to allow the battery voltage to approach a control voltage. That is, the control voltage is set to an acceleration control voltage higher than the battery voltage by a predetermined voltage difference xcex94V1, within a range of voltages higher than the battery voltage and less than the steady state control voltage, during a acceleration during low speeds with the rotational speed of the engine being equal to or less than a predetermined value and a rate of increase in the rotational speed being equal to or greater than a predetermined value.
In another aspect of the invention, the resistance potential divider circuit for outputting a plurality of voltages is used to form an acceleration control voltage and a deceleration control voltage. The voltages are then selected by a plurality of switches (an analog multiplexer may also be employed).
In another aspect, the switch control circuit determines which one of the switches is to be selected, according to the rotational speed of the engine sensed according to a voltage of one phase output from an output terminal of the armature coil.
In another aspect of the invention, a delay time in response to control during acceleration during low speeds is made greater than a delay time in response to control during deceleration during low speeds. This prevents a sudden decrease in output current of the alternator during acceleration, or a sudden drop in alternator torque. This makes it possible to avoid sudden charging of the battery during acceleration and provides further improved stability in the rotational speed of the engine.
In another aspect, the control means has a delay circuit for determining a delay time in response to control during acceleration during low speeds. Moreover, the delay circuit is turned off during deceleration during low speeds.
In another aspect of the invention, the controller sets the control voltage to an acceleration control voltage that is higher than the battery voltage by a predetermined voltage difference xcex94V1, within a range of voltages higher than the battery voltage and less than the steady state control voltage, during a acceleration during low speeds with the rotational speed being equal to or less than a predetermined value and a rate of increase in the rotational speed being equal to or greater than a predetermined value. This control can be called a mode for suppressing rates of increase in battery voltage or a charge suppression mode. Control of this type may be executed prior to control which employs the steady state control voltage as a control voltage, thereby preferably realizing control.
That is, according to this control, the control voltage is set higher than the battery voltage by a predetermined voltage difference xcex94V1 in the recovery process of the rotational speed of the engine. In this process, the rotational speed of the engine and the battery voltage are decreased due to the connection of electrical loads, and the rotational speed of the engine is increased due to an increase in fuel injection provided subsequently by the engine control system. Also, the predetermined voltage difference xcex94V1 ranges from 0.1V to 0.15V, and may be kept at a constant value during acceleration during low speeds. Alternatively, for example, the difference may be increased from the earlier stage to the later stage of acceleration during low speeds.
In another aspect, the control voltage is further set to a deceleration control voltage lower than the battery voltage by a predetermined voltage difference xcex94V2. This is carried out after the rotational speed of the engine has decreased below a first predetermined rotational speed value N1 within a period of deceleration during low speeds immediately preceding the aforementioned acceleration during low speeds. The control of this type can be referred to as a battery voltage drop adjustment mode or a discharge supression mode which means not more than the control of discharge of the battery. Moreover, the control is desirably executed prior to the control which employs the steady state control voltage as a control voltage. The predetermined voltage difference xcex94V2 ranges from 0.1V to 0.15V, and may be kept at a constant value during deceleration during low speeds. Alternatively, for example, the difference may be increased being operatively associated with a decrease in rotational speed of the engine or a drop in battery voltage.
That is, this arrangement employs a gradual decrease in control voltage at the time of deceleration like the acceleration control voltage in the aforementioned claim 1. This is carried out at the later stage of said period of deceleration during low speeds in which a smaller amount of the alternator output and the torque produced by the engine is provided. The control voltage is thereby maintained to prevent the battery from being discharged while the rotational speed of the engine has decreased slightly and allowable power generation capacity is available at the earlier stage of during deceleration during low speeds. When the rotational speed of the engine decreases more than this, the control voltage is decreased, being operatively associated with a drop in battery voltage which requests that the battery discharges. Also, this arrangement does not allow the control voltage to be reduced at once even after the rotational speed of the engine has been decreased below the first predetermined rotational speed value N1. For this reason, the drive torque (load torque) of the alternator will not be suddenly changed.
In another aspect of the invention, the predetermined voltage difference xcex94V1, between a voltage given at a minimum rotational speed value Nmin, at which during deceleration during low speeds is shifted to acceleration during low speeds, and a voltage at the subsequent rotational speed of the engine being equal to or greater than a second predetermined rotational speed value N2, is set to a voltage less than the predetermined voltage difference xcex94V1 during the subsequent acceleration during low speeds. Accordingly, power generation and charging of the battery are prevented to increase the rotational speed of the engine at the earlier stage in the recovery process of the rotational speed of the engine where the outputs of the engine torque and the alternator are not sufficient. At the same time, a sudden increase in drive torque (load torque) of the alternator viewed from the engine is prevented when during deceleration during low speeds is shifted to acceleration during low speeds. Furthermore, a sudden increase in battery charging current is prevented. This makes it possible to realize a smooth increase in engine load torque.
In another aspect, the control voltage is set to a deceleration control voltage less than the battery voltage by the predetermined voltage difference xcex94V2. This is carried out during a period of deceleration during low speeds with the rotational speed, immediately preceding the rotational speed of the engine is increased, being equal to or less than a predetermined value and the rate of decrease in rotational speed being equal to or greater than a predetermined value.
This prevents sudden increase in drive torque (load torque) of the alternator viewed from the engine, and the predetermined voltage difference xcex94V2 increases at a later stage rather than at an earlier stage of during deceleration during low speeds. Thus, the battery is prevented from being discharged by generating a relatively large amount of power by the alternator. This is done at the earlier stage of acceleration during low speeds with a drop in rotational speed of the engine being still small. That is, it is done when the engine torque and the output of the alternator are still sufficient. On the other hand, consider the later stage of acceleration during low speeds where a smaller drop occurs in rotational speed of the engine, that is, when the engine torque and the output of the alternator have become insufficient. In this stage, power generation by the alternator is relatively strongly prevented to compensate for shortage in power by discharging the battery, thereby preventing a sudden drop of the rotational speed of the engine.
Here, the controller for allowing the battery voltage to approach a control voltage can be comprised of first setting means for setting the control voltage to a predetermined steady state control voltage, and second setting means for setting the control voltage to an acceleration control voltage higher than the battery voltage by a predetermined voltage difference xcex94V1, within a range of voltages higher than the battery voltage and less than the steady state control voltage, during a acceleration during low speeds with the rotational speed of the engine being equal to or less than a predetermined value and a rate of increase in the rotational speed being equal to or greater than a predetermined value.
To achieve the aforementioned object, the following method can be employed in a method for controlling a motor vehicle alternator wherein a rotational speed of an engine and a battery voltage are input, and field current is controlled so as to allow the battery voltage to approach a control voltage. That is, the control voltage is set to an acceleration control voltage higher than the battery voltage by a predetermined voltage difference xcex94V1, within a range of voltages higher than the battery voltage and less than the steady state control voltage, during a acceleration during low speeds with the rotational speed of the engine being equal to or less than a predetermined value and a rate of increase in the rotational speed being equal to or greater than a predetermined value.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are intended for purposes of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. In the drawings: